The present invention relates to a charged beam drawing method and a charged beam drawing apparatus for performing drawing on a mask or a wafer with use of a charged beam to manufacture a semiconductor device, and particularly, to a charged beam drawing method and a charged beam drawing apparatus which adopt a variable shape beam system in which a charged beam shaped and deflected into an arbitrary shape is irradiated on a sample.
Conventionally, to draw an arbitrary pattern on a sample such as a mask or a wafer used for manufacturing a semiconductor device, an electron beam drawing apparatus of a variable shape beam system is used in which an electron beam is shaped into a rectangular or a triangle shape of an arbitrary size, and the beam being focused and deflected is irradiated on the sample.
In this apparatus, due to limitations to the deflection amount with which an electron beam can be deflected, the fields where drawing is allowed without moving a sample are restricted. Therefore, drawing fields are divided into strips each of which has a Y-direction length equal to the maximum deflection amount and has an X-direction length equal to that of a drawing field, and drawing is performed on the entire drawing fields by combining a sequential movement of the sample in the X-direction and a stepped-movement of the sample in the Y-direction.
Further, a small sub-field is set in a maximum deflection field of a main deflector, and sub-deflection is performed at a high speed in the sub-field, thereby to achieve high-speed drawing.
Meanwhile, data which defines a pattern to be drawn is divided for every stripe in compliance with the drawing method system as described above. In addition, to compress the amount of stripe data, the stripe data is divided into small figure groups each being an aggregation of figures drawn by an equal main-deflection amount. In each of the small figure groups, positions of figures in each small figure groups are defined by coordinates relative to the origin of the small figure group.
In a conventional variable shape beam drawing apparatus, sub-fields are set so as to cover the small figure groups, and therefore, the positions of the sub-fields are controlled at random in accordance with the positions of the small figure groups.
In recent years, in accordance with down-sizing of semiconductor elements, it has been prolonged that positions and sizes of figures to be drawn are accurate and that connections at seams between figures are achieved without displacements. As a method of realizing such high accuracy, a multi-pass drawing system is adopted. This system improves the drawing accuracy by an effect of averaging attained by repeatedly drawing one same pattern.
In the multi-pass drawing system, if over-drawing is carried out under same conditions, white noise components are removed so that the drawing accuracy is increased. Further, if a drawing position in a sub-field and a drawing position in a stripe are changed, the drawing accuracy is much more increased since constant tendencies corresponding to the sub-field and the stripe are averaged. In particular, this effect is remarkable at boundaries of sub-fields and strips.
The sub-field multi-pass drawing in which sub-field boundaries are shifted in relation to a pattern figure and the stripe multi-pass drawing in which boundaries of strips are shifted in relation to a pattern figure are realized by preparing data corresponding to the number of times for which the pattern is multi-passed, while changing the data as to the manner of stripe division with respect to a pattern to be drawn and as to the manner of dividing a pattern part in a stripe, into small figure groups.
However, this kind of apparatus has a problem as follows. Specifically, in the system described above in which sub-fields are defined with respect to small figure groups constituting pattern data, there is a case that a sub-field is repeated, depending on the manner of defining the small figure groups.
This means, if pattern positions are adjacent to each other and are defined by different definitions as small figure groups, repetition of sub-field occurs. sub-fields which are regarded to be adjacent as pattern positions are defined by different definitions as small figure groups, repetition of sub-field occurs. Then, even a pattern which can originally be drawn by one sub-field is drawing by a plurality of sub-fields, resulting in a problem that the settling time of a deflector is excessively required and the drawing time is increase. This problem is not limited to a case where multi-pass drawing is carried out, but is common to a case where single drawing is carried out.
Further, to achieve sub-field multi-pass drawing and stripe multi-pass drawing in a charged beam drawing apparatus using a variable shape beam vector scanning system, as described above, different pattern data must be newly prepared for the number of times for which a pattern is multi-passed, changing the manner of stripe division and the manner of division of small figure groups with respect to a pattern to be drawn, so that burdens required for data processing and for data transmission are large. In addition, when the number of times for which a pattern is multi-passed is changed, all patterns to be multi-passed must be newly prepared.
Thus, in a conventional system in which sub-fields are defined for small figure groups constituting pattern data, there is a problem that repetition of sub-fields occurs and the settling time of a deflector is required excessively, so that the drawing time is increased. In addition, to perform sub-field multi-drawing and stripe multi-drawing, different pattern data must be newly prepared for the number of times for which a pattern is multi-passed.
The present invention has been made in view of the above situation, and has an object of providing a charged beam drawing method which realizes sub-field multi-drawing and stripe multi-drawing only with use of one piece of drawing pattern definition data, without involving large repetition of sub-fields and without preparing data in compliance with the number of times for which a pattern is multi-passed.
Further, the present invention has another object of providing a charged beam drawing apparatus which realizes sub-field multi-drawing and stripe multi-drawing only with use of one piece of drawing pattern definition data, without involving large repetition of sub-fields and without preparing data in compliance with the number of times for which a pattern is multi-passed.